This came out of #4926 - the scope of which was refined to an initial step which is nearly completed by #4991.

This issue is to address the part of the previous issue not yet dealt with - renaming _pixelbuf and adafruit_pypixelbuf to adafruit_pixelbuf so they match for seamless usage. This will simplify the usage in NeoPixel and DotStar, and any future applications.

The current suggestion is to create a new Python library called adafruit_pixelbuf and copy adafruit_pypixelbuf into it (without the colorwheel() code as that is now native to CircuitPython in rainbowio). Then we rename _pixelbuf to adafruit_pixelbuf to match. Simultaneously, we need to update NeoPixel and DotStar to use adafruit_pixelbuf. We also need to ensure that everything is working properly in Blinka.

A discussion about how to do this without breaking current usage must be had before moving forward. I will be discussing this with @dhalbert. I believe as long as we leave backwards-compatible code in NeoPixel and DotStar until 7.0 stable is released, it should be seamless.